Israel declares Jerusalem to be its undivided capital, but the physical evidence inside the city points to a different reality. Jerusalem is a place of checkpoints, security barriers and constant tension between Arab and Jew. Stephen Sackur talks to the city's mayor, Nir Barkat, a self-made tech millionaire who is tipped for a big future in the Likud party. He talks ambitiously about turning Jerusalem into a top global city hosting 10 million tourists a year. How credible is his vision of his city's future?